1) Go for the simple solution and hope that it is only corruption. Download a utility like EASEUS Partition Recovery or Recuva and run it against that drive. DO NOT install them to that drive. Do not boot from that drive. Every write operation makes total data loss more likely. Either take the drive out and work from another machine, or run the utilities from bootable CDs.

2) I hate to say it so late in the game, but you should have backups. Once this issue is resolved, buy at least one external drive and copy everything that you want to keep to it. Repeat with new files regularly. With two external drives, you can use them alternately. Look for threads on backup strategies.

3) If it is indeed physical damage, you may be out of luck. Or at least out a heck of a lot of money, as alt-rtt suggested.

Thanks for prompt replies.I started taking precautions as soon as the hd became slow. But nothing worked. And now it has turned into bad disk. I have tried using different cables and have also plugged it on another pc. But nothing worked.